1. Field of the Invention
The present invention relates generally to a system and method for delivering fuel for combustion in an internal combustion engine. More specifically, the present invention relates to a system and method for utilizing a plurality of fuel delivery assemblies to deliver fuel to each combustion chamber of an internal combustion engine.
2. Description of the Related Art
Generally, an internal combustion engine ignites a mixture of air and combustible fuel within one or more combustion chambers to provide rotational motive force, or torque, to do work. Along with many other factors, optimal performance of an internal combustion engine is dependent upon an adequate supply of fuel for combustion. Two measures of engine performance are illustrative of this dependency: engine torque and engine speed (in revolutions per minute). Generally, the torque produced is proportional to the volume of fuel combusted during a given combustion cycle. That is, under proper conditions, the greater the volume of fuel combusted the greater the force produced from the combustion.
For most applications an engine must be able to provide torque at various speeds as well. For engine speed to increase the flow rate of fuel to the combustion chambers must also increase. Increasing the speed of the engine, however, shortens the time for each combustion cycle. Thus, a fuel delivery system must provide fuel for each combustion cycle at increasingly faster rates as the engine speed is increased. Engine torque and speed can both be limited by the inability of the fuel delivery system to provide fuel at these increasingly faster rates. Engine torque can be limited by an inability to supply the engine with a sufficient volume of fuel for the combustion cycle. Engine speed can be limited by the inability to supply the required volumes of fuel at the needed rate.
In addition to combustible fuel, oxygen is also necessary for combustion. There are various methods of providing fuel and oxygen for combustion to a combustion chamber. The surrounding air, typically, acts as the source of oxygen. An air intake draws in the surrounding air, which is mixed with the fuel. Some delivery systems mix air and fuel before the two substances are delivered to the combustion chamber. Alternatively, the fuel and air can be delivered separately and mixed within the combustion chamber. Some systems use carburetors to draw fuel vapor into an air stream that is then fed into the combustion chamber, while other systems use fuel injection to produce fuel vapor from a liquid fuel spray.
There are many current systems and methods of fuel injection. Typically, a programmable logic device controls the operation of the fuel injection system. One or more pumps are used to produce a source of pressurized fuel. A fluid actuator, sometimes a solenoid operated valve, initiates a flow of pressurized fuel to an injection nozzle. In other applications the fluid actuators include a pump that produces a surge in fuel pressure. The surge in fuel pressure causes an injection nozzle to open, allowing pressurized fuel to flow through the injection nozzle. The shape of the outlet of the injection nozzle contributes to the atomization of the fuel as it exits the injection nozzle. Still other fuel injection systems use an integrated pump and injection nozzle assembly.
One method of fuel injection is direct fuel injection. In direct fuel injection liquid fuel under pressure is injected by a fuel injector directly into a cylinder before combustion is initiated in the cylinder by a spark plug. The fuel injection system converts the liquid fuel into an atomized fuel spray. The atomization of the liquid fuel effectively produces fuel vapor, aiding in the ignition of the vapor during combustion in the cylinder. Increasing the pressure of the fuel also increases the atomization of the fuel when injected into a cylinder.
Typically, the fuel delivery system is sized to provide adequate fuel volumes and flow rates for the normal expected range of engine torque and power needs. However, the fuel delivery system may be unable to supply the fuel volumes and rates at engine speeds, torque and power levels above the normal expected range. Thus, it may arise that engine torque, speed and power are limited by the ability of the fuel delivery system to supply fuel for combustion. This is particularly the case when fuel delivery systems for one type of engine are applied to higher performance engines, with correspondingly higher fuel volume and flow rate requirements dictated by higher torque, speed and power capabilities.
One option to prevent the fuel delivery system from being a limiting component is to oversize the fuel delivery system so that it is capable of delivering far more fuel than could ever be needed. However, oversizing the fuel delivery system is an inefficient method of operation as the oversized system generally far outstrips the normal requirements. Therefore, it would be beneficial to have a fuel delivery system that can more efficiently deliver desired volumes of fuel at desired flow rates over a larger range of desired engine speeds than current fuel delivery systems.
There is a need, therefore, for an improved technique for supplying combustible fuel in internal combustion engines which can be readily adapted to various engine configurations and performance capabilities. There is a particular need for a technique for fuel injection systems that can supply the higher volumetric (i.e. volume per cycle) and flow rate requirements of high performance engines, while permitting manufactures and designers to draw upon certain existing injection system designs and components.